One example of an axial flow rotary machine is a turbofan gas turbine engine of the type used in aircraft. Such engines are mounted on the aircraft by a pylon or similar support structure. The engine and the nacelle which engages the pylon together form the powerplant for the aircraft. The nacelle circumscribes the turbofan engine to form an enclosed shelter for the engine, with the nacelle aiding the pylon in supporting the turbofan engine.
The turbofan engine powerplant has a compression section, a combustion section, and a turbine section. A primary flow path for working medium gases extends axially through the sections of the engine. The flow path is annular. An inner casing and an outer casing extend axially through the engine to bound the primary flow path. A secondary flow path for working medium gases extends axially through the engine and outwardly of the primary flow path. The secondary flow path is annular. The outer casing of the primary flow path inwardly bounds the secondary flow path. A second casing outwardly of the outer casing, outwardly bounds the secondary flowpath. The second casing is commonly called the fan casing. Radially extending struts extend between these casings to support and position the casings with respect to each other.
The nacelle has a nacelle inner body which extends axially to meet the outer casing and continues the inner boundary of the secondary flow path. The nacelle inner body has circumferentially extending doors which are hinged at the top of the nacelle and secured at the bottom to provide access to the engine through the nacelle. An example of such a construction is shown in U.S. Pat. No. 4,549,708 issued to Norris entitled Cooling Latch System which is assigned to the assignee of this application.
Because the nacelle is a structural element of the powerplant, the nacelle must transmit loads under operative conditions to the pylon which supports both the engine and the nacelle. These nacelle loads are transmitted in part directly from the nacelle to the pylon and transmitted inpart indirectly to the pylon through the engine. The engine has a radially extending stator structure which includes struts for receiving these nacelle loads and which provide a support for the engine. In addition, the interior of the nacelle is sealed to isolate the interior from the fan bypass duct. Accordingly, the nacelle engages the engine at a structure which can accept such loads while providing a seal at the interface.
In modern engines, the inner body of the nacelle typically engages a circumferentially extending ring. The ring provides a seal land which engages the circumferentially extending doors of the nacelle and is a structural member for transmitting part of the nacelle loads to the engine. This ring is held in place with fasteners such as bolts or rivets requiring holes which give rise to stress concentrations in the structure.
As a result, scientists and engineers working under the direction of Applicant's assignee have sought to construct a stator structure for receiving loads from the nacelle through a structure which accepts loads but which does not require that the structure be an integral part of a casing or require holes for fasteners that give rise to stress concentrations. In addition, it is important to provide the engine with a stiff stator structure while minimizing the impact that such structures have on the weight of the engine.